This invention relates to a switch apparatus including a movable contact carrier having a bridging contact means selectively engaging spaced contacts and particularly to a push-pull type switch.
Electrical circuits include various switches for opening and closing circuits. One highly developed switch apparatus includes spaced contacts mounted on a suitable support and connected to the circuit leads. A bridging contact is secured to a carrier which is movably mounted on the support and is mechanically positioned in an aligned and bridging position engaging with the spaced contacts or alternately in a non-bridging position spaced from such contacts. In a practical application of such an apparatus, a supporting housing on casing is provided having a contact support wall to which the spaced contacts are secured with internal contacts and external terminals. A contact carrier is slidably supported within the casing and includes a spring-loaded contact plate having a bridging contact urged into sliding engagement with the interior of the flat wall. A push-pull rod is journaled within an opening in the casing with the inner end affixed to the carrier and the outer end formed with a convenient operating knob. Such switches are often used in "blind" applications. For example, such push-pull switches may be secured to a vehicle dashboard. The casing includes a threaded mounting hub formed to the front wall and supporting the operating rod. The hub projects through a dash-board opening and is secured in place by a clamping nut. The knob or handle on the exterior end of the actuating rod is releasably attached as by a threaded connection to permit assembly of the clamping nut to the threaded hub. Various other switch units are similarly constructed with relatively fixed contacts and a movable bridging contact unit.
Reference may be made to the following U.S. Pat. Nos. 2,521,561, 3,198,896 and 3,903,390 for a general disclosure of various switch structures.
The electrical switch art is of course a highly developed technology and generally satisfactory and low cost switch structures are available. However, the switch structures have a finite life, and a particular area of failure exists in the movable contact structures. Thus, conventional push-pull switch units do not operate satisfactorily for example, for a range of 50,000 cycles even though such usage is not unexpected in various applications. Further, push-pull switches are reasonable expensive because of the actuating rod structure and its fixed connection to the carrier.